Lithium diffusion pathways and vacancy formation in the Pmmn-Li(1-x)FeO2 electrode material

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Li(1-x)FeO(2) is a promising electrode material for lithium ion batteries.
• Understanding Li(+) ion mobility is crucial for optimizing battery performance.

Purpose of the Study:

• To model and investigate Li(+) ion mobility in the orthorhombic phase of Li(1-x)FeO(2).
• To explore the impact of lithium vacancies on ion transport and conductivity.

Main Methods:

• First-principles Density-Functional-Theory (DFT) calculations using the B3LYP functional.
• Supercell construction and full least-energy structure optimization.
• Analysis of ion diffusion pathways, energy barriers, and electronic structure.

Main Results:

• In defect-free LiFeO(2), ion diffusion is cooperative, with Li ions moving through a fraction of active layers.
• Energy barriers for Li(+) ion hopping were determined for tetrahedral and linear bottleneck states.
• In Li(0.75)FeO(2), favorable ion transport mechanisms with lower energy barriers (0.292 and 0.304 eV) were identified.
• Ionic conductivity increased significantly from 10(-5)-10(-6) ohm(-1) cm(-1) in LiFeO(2) to 4 × 10(-4) ohm(-1) cm(-1) in Li(0.75)FeO(2).

Conclusions:

• Lithium vacancies in Li(1-x)FeO(2) create more efficient ion transport pathways, enhancing ionic conductivity.
• The corrugated layer orthorhombic phase of Li(1-x)FeO(2) shows potential for improved lithium ion battery electrodes.
• Computational modeling provides valuable insights into ion mobility mechanisms and material design for batteries.